Muscle spindles as pain receptors

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2023-06-15
Major/Subject
Mcode
Degree programme
Language
en
Pages
4
1-4
Series
BMJ Neurology Open, Volume 5, issue 1
Abstract
Background Muscle membranes have a sensation of pain, but within the muscle tissue, the origin of pain is unclear. We present a hypothesis that the pain receptors of the muscle tissue are situated principally in the muscle spindles. A recent report reintroduced that € end plate spikes' in needle electromyography (EMG) are fusimotor unit potentials of the intrafusal muscle fibres, and thus represent a marker of muscle spindles. Methods We studied four relaxed muscles with 50 EMG needle insertions in each and mapped the appearance of pain and spontaneous EMG activity. Results Only 4.0% of the needle insertions in muscle tissue elicited pain. However, needle insertions in local active points showing € end plate spikes' and, thus, fusimotor unit potentials of the muscle spindles elicited pain in 86% of the insertions, whereas needle insertions in points without € end plate spikes' elicited pain in only 1.0% of the insertions (p<0.001). Conclusions Muscle spindles have pain receptors. The extrafusal muscle tissue is practically pain-free for the needle insertions. This demonstrates a scarcity of extrafusal pain receptors. How this observation is put into perspective with the muscle pain syndromes was discussed.
Description
Publisher Copyright: © Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.
Keywords
EMG, NEUROMUSCULAR, PAIN
Other note
Citation
Partanen , J V , Lajunen , H R & Liljander , S K 2023 , ' Muscle spindles as pain receptors ' , BMJ Neurology Open , vol. 5 , no. 1 , e000420 , pp. 1-4 . https://doi.org/10.1136/bmjno-2023-000420